I got a book recently that you might want to look at:
_History of the Indian Tribes of Hudson's River_ by E.M. Ruttenber,
originally written in 1872, but reprinted in 1992 by Hope Farm Press.
It's an inexpensive book, but has more on the Esopus than anything I've
ever seen (especially the Handbook of North American Indians!). Though
written in the late 1800s, it is relatively sympathetic to the Native
people themselves, and does a nice job of blaming the Dutch for their
genocidal wars against the people of the lower Hudson River. There are
also chapters on traditional culture which I haven't really looked at.
Another good one is _The Lenape_ by Herbert Kraft, 1986. He talks about
the people of that region, but is not so specific about the Esopus.
Last, C.A. Weslager's _the Delaware_ 1972, not so good as Kraft.
Hope these are of some help to you. I'd be curious to here about your
interest in the Esopus.
Ann McMullen
Curator of North American Ethnology
Milwaukee Pubic Museum
annmcm@mpm1.mpm.edu